When electronic documents are transmitted in networks, these documents should be protected against undesirable access. This concerns the end users (that is those for whom an electronic document is intended, hereinafter called users) and also system administrators of the user's computer, or “bad guys”. For example, the user should be prevented from printing the document, forwarding it or storing it. System administrators should be prevented from being able to access the document despite having full read permissions on the user's computer. The “bad guys” can comprise hackers who want to create access to the user's computer, persons who are attempting to intercept the data traffic between the client (user's computer) and server (“data space”), as well as viruses, worms and trojans.